Catholics believe that Mary, the mother of Jesus, became pregnant not through a sexual encounter with a man, but by the power of the Holy Spirit. Joseph was betrothed to a woman who was pregnant and he knew he was not the father. He was troubled. God spoke to Joseph in a dream telling him, “that which is conceived in her is of the Holy Spirit.” (Matthew 1:20)
Many people, when they encounter this piece of Catholic tradition, have doubts that it could happen. Some even point to other pagan gods being born of virgins and suggest the possibility that Catholicism borrowed from these legends — especially since there is no mention of Mary’s virginity in Mark’s Gospel, the oldest of the four gospels.
The Catechism of the Catholic Church, however, states the following:
Some might wonder if we were merely dealing with legends or theological constructs not claiming to be history. To this we must respond: Faith in the virginal conception of Jesus met with the lively opposition, mockery or incomprehension of non-believers, Jews and pagans alike;151 so it could hardly have been motivated by pagan mythology or by some adaptation to the ideas of the age. The meaning of this event is accessible only to faith, which understands in it the “connection of these mysteries with one another.”